1. Field of the Invention
The present invention relates to an imaging apparatus with an autofocus function that automatically focuses on a subject, an imaging method, a program, and an integrated circuit.
2. Description of the Related Art
A multiple-sensor structure imaging apparatus using a color-separating prism is one example of a conventional imaging apparatus, such as a video camera. Such an imaging apparatus has a branch optical path from which a light beam is emitted, in addition to optical paths for light beams into which the incident light is split according to colors. To generate a signal that is used to focus an imaging lens, which is mounted on the camera body, the imaging apparatus includes an image sensor on the light emitting surface of the branch optical path. A driving means moves an element arranged on the light emitting surface of the branch optical path in the optical axis direction to enable the autofocus (hereafter referred to as “AF”) function of the imaging apparatus (see, for example, Patent Citation 1). The imaging apparatus with the AF function has three optical-path channels respectively for a blue light beam, a red light beam, and a green light beam, into which light entering through the lens is divided according to the colors, and additionally has another optical-path channel for a light beam separated from the green light beam. The three optical-path channels are used to obtain a color video signal. The branch optical path is used to obtain a focal point detection signal. The imaging apparatus with this structure can automatically adjust an “in-focus” position by moving the image sensor arranged for focal point detection along the optical axis and using the branch optical path that does not affect a video signal. When detecting an in-focus position using a video signal generated for imaging-purpose, an imaging apparatus usually performs a wobbling operation of slightly moving its focus lens back and forth. In this case, the imaging apparatus has only a limited capability in detecting an in-focus position because the imaging apparatus is required to minimize effects of the in-focus position detection on a video signal. However, the above-described imaging apparatus with the AF function can detect an in-focus position without affecting a video signal, and therefore can detect an in-focus position with a higher precision. Also, the above-described imaging apparatus with the AF function can employ various methods for detecting an in-focus position.
Patent Citation 1: Japanese Unexamined Patent Publication No. H8-50227